Having developed phosphorus nuclear magnetic resonance (31P NMR) to the study of phosphate containing metabolites in perfused beating heart, the aim of the work in the second two years is to investigate functioning and damage cardiac tissue by this powerful new technique. Rates of metabolic processes will be measured in three ways. (1) during changing metabolic conditions the concentrations of the major phosphate containing metabolites and intracellular pH will be followed with a time resolution of 20-30 sec; (2) in the steady state saturation transfer NMR (a recently developed technique) will be used to measure rapid reactions such as the ATP to phosphocreatine interconversion; (3) by synchronizing data acquisition with different intervals of the contraction relaxation cycle of the heart, fluctuations in the associated biochemical events and in their rates will be followed. These will aid our understanding of the bioenergetic requirements of the heart. Under various conditions of low oxygen supply (ischemia, hypoxia, and anoxia) 31P NMR will be applied to measure quantitatively the volume of anoxic regions compared to normoxic ones, thus providing a detailed insight into the events during heart-infarct. This work will be fully integrated with complementary studies using fluorescence and biochemical techniques (being carried out in Philadelphia). The application of this powerful technique will thus help in the search to understand the conditions of the normal and diseased heart and will lead to the design of new therapeutic procedures.